The RT5751A/B is a simple, easy-to-use, 1A synchronous step-down DC-DC converter with an input supply voltage range from 2.5V to 6V. The device build-in an accurate 0.6V reference voltage and integrates low RDS(ON) power MOSFETs to achieve high efficiency in a WDFN-6L 2x2 package.

The RT5751A/B adopts Advanced Constant On-Time (ACOT®) control architecture to provide an ultrafast transient response with few external components and to operate in nearly constant switching frequency over the line, load, and output voltage range. The RT5751A operate in automatic PSM that maintain high efficiency during light load operation. The RT5751B operate in Forced PWM that help to meet tight voltage regulation accuracy requirements.

The RT5751A/B senses both FETs current for a robust over-current protection. The device features cycle-by-cycle current limit protection and prevent the device from the catastrophic damage in output short circuit, over current or inductor saturation. A built-in soft-start function prevents inrush current during start-up. The device also includes input under-voltage lockout, output under-voltage protection, and over-temperature protection to provide safe and smooth operation in all operating conditions.


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  • General Purpose for POL LV Buck Converter
Key Spec.
RT5751A RT5751B
Status Active Active
Vin (min) (V) 2.5 2.5
Vin (max) (V) 6 6
Number of Outputs 1 1
Vout (min) (V) 0.6 0.6
Vout (max) (V) 6 6
Output Adj. Method Resistor Resistor
Iout (max) (A) 1 1
Current Limit (typ) (A) 2.65 2.65
Freq (typ) (kHz) 1500 1500
Ext Sync No No
Ron_HS (typ) (mOhm) 120 120
Ron_LS (typ) (mOhm) 80 80
Iq (typ) (mA) 0.025 0.3
Features 100% Duty Cycle;ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Internal Compensation;OCP;OTP;PSM;Power Good;Stable with Ceramic Capacitor;UVP 100% Duty Cycle;ACOT Control;Cycle-by-Cycle Current Limit;Enable Input;Fast Transient Response;Force PWM;Internal Compensation;OCP;OTP;Power Good;Stable with Ceramic Capacitor;UVP
Package Type WDFN2x2-6 WDFN2x2-6
  • Input Voltage Range from 2.5V to 6V
  • Integrated 120mΩ and 80mΩ FETs
  • 1A Output Current, up to 95% Efficiency
  • 100% Duty Cycle for Lowest Dropout
  • 1% Internal Reference Voltage
  • 1.5MHz Typical Switching Frequency
  • Power Saving Mode for Light Loads (RT5751A)
  • Low Quiescent Current: 25μA (Typ.)
  • Fast Advanced Constant On-Time (ACOT®) Control
  • Internal Soft Startup (0.6ms)
  • Enable Control Input
  • Power Good Indicator
  • Both FETs Over-Current Protection
  • Negative Over-Current Protection (RT5751B)
  • Input Under-Voltage Lockout Protection
  • Hiccup-Mode Output Under-Voltage Protection
  • Over-Temperature Protection
  • RoHS Compliant and Halogen Free
TitleLast UpdateDownload
6V 1A, ACOT® Buck Converter2021/07/07
Reference Design
TitleLast UpdateDownload
Richtek Load Transient Tool2022/07/25
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT5751AHGQWWDFN2x2-63000 Request Buy from Distributor